Vacuum interrupter shunted with mechanical switch

ABSTRACT

An electric circuit breaker for switching capacitive loads, such as capacitor banks or long electric power transmission lines, comprises a metallic housing having a pair of spaced apart terminal bushings extending through the wall thereof. Each bushing comprises a conductor and an insulator. A vacuum interrupter comprising an evacuated envelope and a stationary and a movable contact therein is mounted in the housing between the bushings and each contact is connected to the conductor in a respective bushing. A shunting switch for parallel connection with the vacuum interrupter is mounted in the housing between the bushings. The shunting switch has less current interrupting capacity but greater current carrying capacity than the vacuum interrupter. The shunting switch comprises a stationary contact which is mounted on one bushing and electrically connected to the conductor therein. The shunting switch further comprises a pivotable blade type contact which is mounted on the other bushing and electrically connected to the conductor therein. Operating means are located in the housing and comprises a first and second insulated contact rods which are connected to the movable contact of the vacuum interrupter and the blade of the shunting switch, respectively. In operation, the operating means causes the vacuum interrupter to close before and open after the closing and opening, respectively, of the shunting switch.

United States Patent Brunner 1 June 20, 1972 [54] VACUUM INTERRUPTERSHUNTED WITH MECHANICAL SWITCH [7 21 Inventor: Richard G. Brunncr,Dedham, Mass.

[73] Assignee: Allis-Chalmers Manufacturing Company,

Milwaukee, Wis.

22 Filed: Nov. 16,1970

211 Appl.No.: 89,893

[56] References Cited UNITED STATES PATENTS 1,783,279 12/1930 Burnham..200/l44 B 2,480,622 8/1949 Wamock 3.560,682 2/197] Kohler et a]..200/l44 B Primary Examiner-Robert S. Macon Attorney-Thomas F. Kirby,Robert B. Benson and Lee H. Kaiser [57] ABSTRACT An electric circuitbreaker for switching capacitive loads, such as capacitor banks or longelectric power transmission lines, comprises a metallic housing having apair of spaced apart terminal bushings extending through the wallthereof. Each bushing comprises a conductor and an insulator. A vacuuminterrupter comprising an evacuated envelope and a stationary and amovable contact therein is mounted in the housing between the bushingsand each contact is connected to the conductor in a respective bushing.A shunting switch for parallel connection with the vacuum interrupter ismounted in the housing between the bushings. The shunting switch hasless current interrupting capacity but greater current carrying capacitythan the vacuum interrupter. The shunting switch comprises a stationarycontact which is mounted on one bushing and electrically connected tothe conductor therein. The shunting switch further comprises a pivotableblade type contact which is mounted on the other bushing andelectrically connected to the conductor therein. Operating means arelocated in the housing and comprises a first and second insulatedcontact rods which are connected to the movable contact of the vacuuminterrupter and the blade of the shunting switch, respectively. Inoperation, the operating means causes the vacuum interrupter to closebefore and open after the closing and opening, respectively, of theshunting switch.

1 Claim, 2 Drawing Figures BACKGROUND OF THE INVENTION l. Field of theInvention This invention relates generally to electric circuit breakersand particularly to those which comprise vacuum type interrupters orswitches.

2. Description of the Prior Art Vacuum interrupters and switches areinherently wellsuited for duty in switching capacitive loads, such ascapacitor banks or long transmission lines. However, vacuum interruptersand switches have extremely high momentaryarc current interruptingcapabilities which very often exceed their continuous current carryingcapabilities. It was the practice, therefore, to rely on vacuuminterrupters and switches for switching capacitive loads and to rely onother types of circuit breakers for carrying and interrupting highcurrent loads, such as metal-clad breakers using magnetic blow-outprinciples or oil type circuit interrupters. However, these other typesof circuit breakers require more maintenance and more space-than vacuuminterrupters and, frequently, need to be used in addition to vacuuminterrupters and switches. It is desirable, therefore, to provide newand improved circuit breakers which provide the inherent I advantages ofvacuum interrupter and switches and the current carrying capabilities ofother types of circuit breakers but which are smaller, less costly andsimpler than installations which merely combine both types of switches.

SUMMARY OF THE INVENTION In accordance with the present invention thereis provided a new and improved electric circuit breaker which comprisesa vacuum type circuit interrupter or switch having a sealed envelope anda pair of relatively movable interrupter contacts therewithin. Anair-break shunting switch comprising relatively movable shuntingcontactsis connectedin parallel with the vacuum interrupter. Theshunting switch has less interrupting capacity but greater currentcarrying capacity than the vacuum interrupter. Operating means connectedto the vacuum interrupter and to the shunting switch effect closure ofthe interrupter contacts prior to closure of the shunting contacts andopening of the interrupter contacts after opening of the shuntingcontacts.

In a preferred embodiment of the invention, a metallic housingisprovided which has at least one pair of spaced apart terminal bushingsextending through thewall thereof. Each terminal bushing comprises aninsulator with a conductor extending therethrough. The vacuuminterrupter and theshunting switch are supported inside the housingbetween the bushings. An operating means is mounted inside the housingand comprises insulating rods which are connected to the movablecontacts of the vacuum interrupter and the shunting switch.

OBJECTS It is an object of the present invention to provide improvedelectric circuit breakers which afford the arc interrupting advantagesof vacuum interrupters and the greater current carrying capabilities ofother types of switches but which are more compact, more economical,more reliable, and longer-lived than conventional installations whichmerely combine various types of switches and interrupters.

Another object is to provide circuit breakers of the aforesaid characterwhich are well-adapted for use in a wide variety of specificapplications in electrical power transmission and distribution systems.

Another object is to provide such circuit breakers which includecommercially available components and a minimum number of custom-madeparts.

Other objects and advantages of the invention hereinafter appear.

will

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing illustrates apreferred embodiment of the invention but it is to be understood thatthe embodiment illustrated is susceptible of modification with respectto details thereof without departing from the scope of the appendedclaims.

In the drawing:

FIG. 1 is a side elevational view of the=interior of a circuit breakerin accordance with the present invention; and

FIG. 2 is an end elevational view in reduced scale of one end of theexterior of the circuit breaker shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2 of.the drawing, the numeral 10 designates a circuit breaker in accordancewith the present invention. Circuit breaker 10 is a multipole devicecomprising a metallic housing or enclosure. 12 containing three poleunits 14,716 and 18 and is understood, for example, to be adapted foruse in a three phase a.c. high voltage, high current electriapartterminal bushings 20 and 22 which extend through wall 24 of housing. 12.Bushings 20 and 22 comprise conductors 26 and 28, respectively, whichextend through insulated portions 30 and 32, respectively, of thebushings.

Ari-electric circuit interrupter 34, such as a vacuum type circuitinterrupter or vacuum switch, is disposed between the bushings 20 and 22inside housing 12. Interrupter 34 comprises a sealed envelope36 in whicha vacuum is maintained and further comprises a pair of relativelymovable contacts within the envelope, such as a stationary contact 38and a movable contact 40. interrupter '34 is shown in circuit openposition in FIG.'1.

Means are provided for mounting interrupter 34 between the bushings 20and 122 and comprise a metallic bracket or support 42 which is rigidlymounted on the inner end of bushing 22. Interrupter 34 is rigidlysecured at one end to bracket 42 as by bolts 44.In this manner,interrupter 34 is insulated from housing 12.

Means are provided for electrically connecting the contacts 38 and 40,respectively, of interrupters 34 to the conductors 26 and 28,respectively, of the terminal bushings 20 and 22, respectively. Thus, afirst electrically conductive terminal block 46 ismounted on conductor26 and is connected by a ry contact 56 which is mounted on andelectrically connected to inner end conductor 26 of bushing 20 bysuitable means, such as terminal block 46. Shunting switch 54 furthercomprises a movable contact 58 in the form of an electrically conductiveswitch blade which is pivotably mounted on a pin 59 carriedon bracket42.

Means are provided for electrically connecting blade contact 58 toconductor 28 of bushing .22 and comprise a flexible conductor 60 whichis connected to blade contact 58 and to second terminal block 50.

Operating means 64 are provided to operate interrupter 34 and shuntingswitch 54 of circuit breaker 10 in accordance with the invention and,preferably, are mounted on and enclosed in housing I2. Operating means64 comprise an enclosure '66 in which an operating linkage 68 is housed.Reciprocably movable insulated operating rods 70 and 72 extend intoenclosure 66 and are connected at their one end to linkage 68 ofoperating means 64. The operating rods 70 and 72 are mechanicallyconnected at their other end to the movable contact 40 of interrupter 34and to the movable contact 58 of shunting switch 54, respectively. Inthe preferred embodiment, operating means 64 effects simultaneousoperation of the pole units l4, l6 and 18.

It is to be understood that linkage 68 of operating means 64 isoperated, when desired, by suitable mechanical or electrical controlmeans 74 which are connected thereto and located, for example,exteriorly of housing 12.

Circuit breaker 10 operates as follows. Assume that circuit breaker 10is in open condition as shown in FIG. 1 and that it is desired to closeit. Further assume that all directions of movement hereinafter referredto are with respect to FIG. 1. A closing signal from control means 74 istransmitted to operating linkage 68 of operating means 64. In responseto this signal, linkage 68 effects upward movement of operating rod 70and closure of contacts 38 and 40 in interrupter 34. Any arcing thatoccurs as the contacts 38 and 40 close is confined within envelope 36 ofinterrupter 34. Subsequent to closure of interrupter 34, linkage 68 ofoperating means 64 effects upward movement of operating rod 72 andclockwise pivotal movement of movable blade contact 58 of shuntingswitch 54. Since the circuit between the bushing 20 and 22 is alreadyclosed by interrupter 34, no arcing occurs between contacts 56 and 58 ofshunting switch 54 as they close. However, since the contacts 56 and 58are larger than the contacts in interrupter 34, switch 54 has greatercurrent carrying capacity than interrupter 34.

Assume now that circuit breaker 10 is in closed condition and that it isdesired to open it. An opening signal from control means 74 istransmitted to operating linkage 68 of operating means 64. In responseto this signal, linkage 68 effects downward movement of operating rod72, counter-clockwise movement of contact 58 and separation of contacts56 and 58 of shunting switch 54. Since interrupter 34 is still closed,no arcing occurs between the contacts 56 and 58 of switch 54 as theypart. Subsequent to opening of shunting switch 54, linkage 68 ofoperating means 64 effects downward movement of operating rod 70 andseparation of contacts 38 and 40 of interrupter 34. Arcing that occursis confined within envelope 36 of interrupter 34.

It will be apparent that circuit breaker 10 has greater current carryingcapacity than interrupter 34 alone and greater interrupting capabilitythan shunting switch 54 alone. However, switch 54 requires no arc chuteor are quenching means, as do comparable prior art air-break switches,which require maintenance or service. Furthermore, enclosure ofinterrupter 34, shunting switch 54 and operating means 64 within housing12 eliminates problems associated with icing and contamination andreduces the possibility of damage to components. All live components areelectrically insulated from housing 12 by the insulators 30 and 32 ofthe bushings 20 and 22, respectively, and by the insulated operatingrods 70 and 72, yet no complicated structure is required.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. An electric circuit breaker comprising:

a metallic housing,

a first terminal bushing comprising an insulator constructed andarranged to extend through a wall of said housing and having a conductorextending through said insulator into the interior of said housing;

a second terminal bushing comprising an insulator constructed andarranged to extend through the wall of said housing in spacedrelationship to said first bushing and having a conductor extendingthrough said insulator thereof into the interior of said housing;

a bracket secured to the inner end of said first bushing and theconductor associated therewith;

an electric circuit interrupter of the vacuum type comprising a sealedenvelope mounted on said bracket; a movable contact extending rnto sardenvelope in movable sealed relationship therewith;

a flexible conductor operably connected to the conductor associated withsaid first bushing and to said movable contact of said interrupterswitch;

a stationary contact extending into said envelope in sealed relationshiptherewith;

a conductor operably connected to the conductor associated with saidsecond bushing and to said stationary contact of said circuitinterrupter;

a shunting switch having a greater current carrying capacity but lessinterrupting capacity than said circuit interrupter, said shuntingswitch comprising a fixed shunting contact secured in operative positionto said conductor of said second bushing, and a movable shunting contactpivotally carried on said bracket for movement into and out ofengagement with said fixed shunting contact;

a flexible conductor electrically connecting said movable shuntingcontact to the conductor associated with said first bushing;

operating means located within said housing, said operating meanscomprising a first insulated rod connected to the movable contact ofsaid circuit interrupter, a second insulated rod connected to saidmovable shunting contact, and operating linkage operably interconnectingsaid first and second insulated rods in a manner that actuation of saidoperating means in one direction effects the movement of said movablecontact of said circuit interrupter to closed position prior toeffecting the pivotal movement of said movable shunt contact to closedposition, and actuation of said operafing means in the oppositedirection effects the pivotal movement of said movable shunting contactto open position prior to moving the movable contact of said circuitinterrupter to open position;

whereby the greater interrupting capacity of said circuit interrupter isalways in circuit prior to the closing and subsequent to the opening ofsaid shunting switch which serves as the main current carrier, and anyarcing occurs between the contacts of said circuit interrupter and isconfined within the sealed envelope thereof.

III III II II!

1. An electric circuit breaker comprising: a metallic housing, a firstterminal bushing comprising an insulator constructed and arranged toextend through a wall of said housing and having a conductor extendingthrough said insulator into the interior of said housing; a secondterminal bushing comprising an insulator constructed and arranged toextend through the wall of said housing in spaced relationship to saidfirst bushing and having a conductor extending through said insulatorthereof into the interior of said housing; a bracket secured to theinner end of said first bushing and the conductor associated therewith;an electric circuit interrupter of the vacuum type comprising a sealedenvelope mounted on said bracket; a movable contact extending into saidenvelope in movable sealed relationship therewith; a flexible conductoroperably connected to the conductor associated with said first bushingand to said movable contact of said interrupter switch; a stationarycontact extending into said envelope in sealed relationship therewith; aconductor operably connected to the conductor associated with saidsecond bushing and to said stationary contact of said circuitinterrupter; a shunting switch having a greater current carryingcapacity but less interrupting capacity than said circuit interrupter,said shunting switch comprising a fixed shunting contact secured inoperative position to said conductor of said second bushing, and amovable shunting contact pivotally carried on said bracket for movementinto and out of engagement with said fixed shunting contact; a flexibleconductor electrically connecting said movable shunting contact to theconductor associated with said first bushing; operating means locatedwithin said housing, said operating means comprising a first insulatedrod connected to the movable contact of said circuit interrupter, asecond insulated rod connected to said movable shunting contact, andoperating linkage operably interconnecting said first and secondinsulated rods in a manner that actuation of said operating means in onedirection effects the movement of said movable contact of said circuitinterrupter to closed position prior to effecting the pivotal movementof said movable shunt contact to closed position, and actuation of saidoperating means in the opposite direction effects the pivotal movementof said movable shunting contact to open position prior to moving themovable contact of said circuit interrupter to open position; wherebythe greater interrupting capacity of said circuit interrupter is alwaysin circuit prior to the closing and subsequent to the opening of saidshunting switch which serves as the main current carrier, and any arcingoccurs between the contacts of said circuit interrupter and is confinedwithin the sealed envelope thereof.